We bought both our TT's new, all our cars were bought new too. We wanted a DP and didn't want to spend an arm and a leg because we don't go away too often; so we started the search for the perfect one for us. We found someone that took immaculate care of their vehicle and it was stored under an awning with all the services up to date and manuals intact. Brand new tires and a GoodSam warranty for a year, (which we continued).
I am saying all this because I feel if you are buying used you really have to be aware of what you're getting (into). You need to know the things that must be done to keep the vehicle in good working order. I feel we were very lucky with our purchase. That isn't always the case, so be very careful of any used motohomes, too much can go wrong. After market warranty's can be just as tricky, read the big print and the small print and get any questions answered in print.
Good Luck!!